Optical device

ABSTRACT

Disclosed is an optical device which includes: an optical component configured to be electrically actuated such that a light transmission state is variable; a driver circuit for the optical component; a power source unit for driving the optical component; a rim for supporting the optical component; a temple having front and rear ends and connected at the front end to the rim; and an earpiece formed at the rear end of the temple. The power source unit includes a secondary battery, a power switch, a power switch control portion, and a use-status sensing portion for sensing the status of use by a user of the optical device. The power switch control portion performs control to turn off the power switch when the use-status sensing portion does not sense any use by the user of the optical device.

RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application No. PCT/JP2011/003153, filed on Jun. 3, 2011,which in turn claims the benefit of Japanese Application No. 2010-148566filed on Jun. 30, 2010, the disclosures of which Applications areincorporated by reference herein.

TECHNICAL FIELD

The present invention relates to optical devices, more specifically to atechnology for extending the service life of a head-worn optical deviceto be worn on the head of a user.

BACKGROUND ART

Some stereoscopic image viewing devices (simply referred to below asviewing devices) generally called 3D eyeglasses or 3D glasses supportactive system and some support passive system.

In the active system, a right-eye image and a left-eye image aredisplayed on a display device, such as a television, while beingalternatingly switched therebetween. On the other hand, on a viewingdevice, liquid crystal shutters or suchlike disposed on right and leftlens portions are alternatingly opened/closed in synchronization withswitching of images on the display device (see Patent Literatures 1 and2).

Display devices used with the active system are structured approximatelyin the same manner as conventional display devices. In addition, simplyusing stereoscopic image data as image data to be displayed on thedisplay devices allows stereoscopic image viewing.

On the other hand, in the passive system, right-eye and left-eye imagesare simultaneously displayed line-by-line on the display device, and inthe display device, a polarizing filter sorts the images for the righteye and the left eye. Then, the sorted images are respectively deliveredto the right eye and the left eye through specialized eyeglasses.Accordingly, in the passive system, 3D images in some cases could not beproperly viewed unless the images are viewed generally in front of thedisplay device. Moreover, since the right-eye and left-eye images aredisplayed on one screen at the same time, the resolution is low.Therefore, for viewing on a household television, the activestereoscopic image viewing system is preferable for users.

However, in the active system, the viewing device is required to includeliquid crystal shutters and a power source for driving them, so that theviewing device becomes heavier and bulkier than normal eyeglasses.Therefore, many users feel discomfort with wearing the viewing device.

Accordingly, active stereoscopic image viewing systems are desired tohave lighter viewing devices for improved comfort of wearing. Currently,it is the mainstream practice to use a small, lightweight, coin-shapedbattery (primary battery) for a drive power source. Also, to achieve alighter viewing device, it is under study to use a laminated battery asa drive power source since laminated batteries can be rendered thinnermore easily than coin-shaped batteries.

Furthermore, attention is drawn by a technology in which eyeglass lensesinclude electroactive elements made of liquid crystals. Current to beapplied to the electroactive elements is adjusted to instantaneouslychange the lenses' diopter (refractive power) or focal point (see PatentLiteratures 3, 4, and 5). This technology makes it possible to achieveeyeglasses (referred to below as variable focus eyeglasses) in which thediopter of myopia correction eyeglass lenses can be partially changed toa diopter for hyperopia correction as necessary or the diopter forapproximately the entire eyeglass lenses can be switched betweendiopters for myopia correction and hyperopia correction as necessary.This makes it possible to achieve a satisfactory field of view withoutdistortion when compared to general, so-called bifocal eyeglasses orsuchlike.

CITATION LIST Patent Literatures

-   Patent Literature 1: Japanese Laid-Open Patent Publication No.    2010-022067-   Patent Literature 2: Japanese Laid-Open Patent Publication No.    2010-020898-   Patent Literature 3: Japanese PCT National Phase Laid-Open Patent    Publication No. 2010-517082-   Patent Literature 4: Japanese PCT National Phase Laid-Open Patent    Publication No. 2009-540386-   Patent Literature 5: Japanese PCT National Phase Laid-Open Patent    Publication No. 2010-522903

SUMMARY OF INVENTION Technical Problem

As described above, so-called 3D eyeglasses often include batteries(secondary batteries) as power sources for driving liquid crystalshutters. In addition, variable focus eyeglasses are planned to includebatteries to obtain current to be applied to liquid crystal materials.However, as with normal eyeglasses, these devices are intended to beworn on the head with their weight supported on the nose and the ears.Accordingly, a significant increase in weight due to inclusion of liquidcrystal shutters and a battery seriously compromises the comfort ofwearing.

To prevent such an increase in the weight of a device with a built-inbattery, it is effective to reduce the weight of the battery to beincluded. However, a reduction in the battery weight results in areduction in capacity. Particularly as for the secondary battery, areduction in capacity often causes the battery to be dischargedcompletely or almost completely (both of such states will becollectively and simply referred to below by being dischargedcompletely) by using the device for a long period of time. The cyclelife of the secondary battery varies in accordance with the depth ofdischarge. The more times it is discharged completely, the shorter thecycle life becomes.

As a result, it is conceivable that the life of the secondary batteryends in about one to two years, for example. Upon such occurrence, ifthe battery is provided in an embedded form, 3D eyeglasses or variablefocus eyeglasses conceivably might need to be replaced in one to twoyears. At present, variable focus eyeglasses are expected to be moreexpensive than normal eyeglasses. Accordingly, the need for replacementby purchase within such a short period of time would not be preferablefor users. On the other hand, the replacement cycle of televisions isgenerally said to be seven to eight years. Accordingly, if the batterylife is one to two years, only the 3D eyeglasses need to be replaced afew times before the television is replaced by purchase. It is verycumbersome for users to order accessories of electronic devices, andtherefore it is desirable to approximate the life of batteries as closeto the replacement cycle of televisions or such like as possible.

Therefore, an objective of the present invention is to achieveappropriate use of a secondary battery, thereby prolonging the life of ahead-worn optical device with optical components electrically actuatedsuch that light transmission states are variable.

Solution to Problem

The present invention is directed to an optical device including:

at least one optical component configured to be electrically actuatedsuch that a light transmission state is variable;

a driver circuit for the at least one optical component;

a power source unit for driving the at least one optical component;

a pair of rims;

a pair of temples having front and rear ends and connected at the frontends to their respective rims; and

a pair of earpieces formed at the rear ends of their respective temples,

the at least one optical component being supported by at least one ofthe rims,

the power source unit including:

a secondary battery;

a power switch;

a power switch control portion; and

a use-status sensing portion for sensing the status of use by a user ofthe optical device, and

the power switch control portion performing control to turn off thepower switch when the use-status sensing portion does not sense use bythe user of the optical device.

For example, the present invention is directed to an eyewear-likestereoscopic image viewing device including:

a right-eye light shutter;

a left-eye light shutter;

a driver circuit for the light shutters;

a power source unit for driving the light shutters;

rims for supporting the light shutters;

temples having front and rear ends, and connected at the front ends tothe rims; and

earpieces formed at the rear ends of the temples,

the power source unit including:

a secondary battery;

a power switch;

a power switch control portion; and

a use-status sensing portion for sensing the status of use by a user ofthe stereoscopic image viewing device, and

when the power switch is on and the use-status sensing portion does notsense any use by the user of the stereoscopic image viewing device, thepower switch control portion turning off the power switch.

Advantageous Effects of Invention

In the present invention, in the case where the power switch is on(power-on) when the optical device is not in use by the user, the powerswitch is automatically turned off (turn-off). Accordingly, even if thesecondary battery is lightweight and has a small capacity, the number oftimes the battery is discharged completely decreases. Thus, it ispossible to prolong the life of the secondary battery or even theoptical device.

While the novel features of the invention are set forth particularly inthe appended claims, the invention, both as to organization and content,will be better understood and appreciated, along with other objects andfeatures thereof, from the following detailed description taken inconjunction with the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an oblique view illustrating the appearance of a stereoscopicimage viewing device as an optical device according to an embodiment ofthe present invention.

FIG. 2 is a functional block diagram of the stereoscopic image viewingdevice in FIG. 1.

FIG. 3 is an oblique view illustrating the appearance of a secondarybattery.

FIG. 4 is an enlarged perspective view of a temple, schematicallyillustrating the configuration of a housing portion for a power sourceunit and a driver circuit.

FIG. 5 is a flowchart showing the operation of a power switch controlportion in the stereoscopic image viewing device of FIG. 1.

FIG. 6 is a top view of a stereoscopic image viewing device as anoptical device according to another embodiment of the present invention,where principal portions of the stereoscopic image viewing device areschematically enlarged in a given state.

FIG. 7 is a top view of the stereoscopic image viewing device as theoptical device according to said another embodiment of the presentinvention, where the principal portions of the stereoscopic imageviewing device are schematically enlarged in another state.

FIG. 8 is a functional block diagram of a stereoscopic image viewingdevice as an optical device according to still another embodiment of thepresent invention.

FIG. 9 is a flowchart showing the operation of a power switch controlportion in the stereoscopic image viewing device of FIG. 6.

FIG. 10 is a diagram schematically illustrating a lens for use invariable focus eyeglasses as an optical device according to yet anotherembodiment of the present invention, as viewed from a directionperpendicular to an incident direction of light.

FIG. 11 is a diagram schematically illustrating a layered structure ofan electroactive element for use in the variable focus eyeglasses.

DESCRIPTION OF EMBODIMENTS

The present invention is directed to an optical device including:

at least one optical component configured to be electrically actuatedsuch that a light transmission state is variable;

a driver circuit for the at least one optical component;

a power source unit for driving the at least one optical component;

a pair of rims;

a pair of temples having front and rear ends and connected at the frontends to their respective rims; and

earpieces formed at the rear ends of the temples.

The at least one optical component is supported by at least one of therims.

The power source unit includes a secondary battery, a power switch, apower switch control portion, a charge/discharge circuit for controllingcharge and discharge of the secondary battery, and a use-status sensingportion for sensing the status of use by a user of the optical device.

When the use-status sensing portion does not sense any use by the userof the optical device, if the power switch is on, for example, the powerswitch control portion performs control to turn off the power switch.

An example of the optical device is an eyewear-like stereoscopic imageviewing device generally called 3D eyeglasses or 3D glasses. Among suchstereoscopic image viewing devices, stereoscopic image viewing devices(also simply referred to below as viewing devices) particularlycompatible with active shutter system include liquid-crystal lightshutters and power source units or such like for driving the shutters,and therefore are heavier compared to normal eyeglasses. Therefore, atpresent, users often feel uncomfortable in wearing the viewing devices.

The secondary battery is used in place of a conventional primarybattery, as a battery for use in the power source unit, therebyeliminating the need for battery replacement, and the secondary batterycan be reduced in size and weight, thereby improving the comfort ofwearing the viewing device.

However, when the secondary battery is reduced in size and weight, thebattery's capacity decreases, which increases the frequency of thebattery being discharged completely or almost completely (this statewill be referred to below simply by being completely discharged). Thecycle life of the secondary battery varies in accordance with the depthof discharge, and the more times it is discharged completely, theshorter the cycle life becomes.

Therefore, there is a need to reduce as much as possible the case wherethe secondary battery is discharged completely. Possible causes of thesecondary battery being discharged completely include the case where theviewing device is continuously used for a long period of time withoutany interruption for recharge and the case where the device is left withthe power switch on. In the latter case, the secondary battery isdischarged in vain.

For example, when the power switch is on and the use-status sensingportion does not sense any use by the user of the optical device, theviewing device of the present invention is left with the power switchon, and therefore the power switch control portion performs control toautomatically turn off the power switch. Thus, the number of times thesecondary battery is discharged completely can be reduced as much aspossible.

As a result, the life of the secondary battery can be prolonged, therebyextending the cycle of replacing the secondary battery. Thus, in thecase where the secondary battery is provided so as not to bereplaceable, such as the secondary battery being embedded in the viewingdevice's frame or suchlike, the cycle of replacing the viewing deviceitself can be extended.

The foregoing is not limited to so-called 3D eyeglasses, and generallyapplies to optical devices designed to be worn on the head (or the face)and including optical components configured to be electrically actuatedsuch that light transmission states are variable. Such optical devicesoften include secondary batteries as power sources for driving opticalcomponents. Accordingly, they share the same challenge of reducing theweight of secondary batteries to be included and preventing the life ofthe secondary batteries from being shortened due to such reduction inweight.

In an aspect of the present invention, the use-status sensing portion ofthe optical device includes a first sensing portion for sensing theoptical device being worn by the user. When the first sensing portiondoes not sense the optical device being worn by the user, if the powerswitch is on, for example, the power switch control portion turns offthe power switch.

Here, the first sensing portion can be configured to include apyroelectric sensor. The pyroelectric sensor may be provided in a givenplace of the optical device where infrared radiation from the human bodycan be sensed. For example, the pyroelectric sensor is provided so as tocontact the skin of the user wearing the optical device, making itpossible to sense the optical device being or not being worn by the userwith high accuracy.

Furthermore, the first sensing portion can be configured to include acapacitive sensor. For example, the capacitive sensor is provided in aportion of the optical device so as to contact the skin of the userwearing the optical device, making it possible to sense the opticaldevice being or not being worn by the user.

In another aspect of the present invention, the optical device has thetemples connected to their respective rims via hinges. In addition,biasing means biases at least one of the temples such that an angularposition of the at least one of the temples about the hinge coincideswith a predetermined angular position corresponding to the opticaldevice's status of not being in use. As the biasing means, an elasticmember such as a spring or rubber can preferably be used. The use-statussensing portion includes a second sensing portion for sensing theangular position of the at least one of the temples to coincide with thepredetermined angular position. When the second sensing portion sensesthe angular position of the at least one of the temples to coincide withthe predetermined angular position, if the power switch is on, forexample, the power switch control portion turns off the power switch.Here, the predetermined angular position corresponding to the opticaldevice's status of not being in use refers to an angular position inwhich the temple is folded about the hinge, for example.

With the above configuration, when the optical device is not worn by theuser, the biasing force of the biasing means causes the at least one ofthe temples to pivot to the predetermined angular position. In thiscase, if the power switch is on, the power switch control portionautomatically turns off the power switch. Thus, a similar effect to thatdescribed above can be achieved.

In still another aspect of the present invention, the optical deviceincludes a reception portion for a signal related to driving of the atleast one optical component. The use-status sensing portion includes athird sensing portion for sensing whether or not the reception portionis receiving the signal. When the third sensing portion does not sensethe reception portion receiving the signal, if the power switch is on,for example, the power switch control portion turns off the powerswitch.

In the active shutter system, a 3D-image display device (such as a 3Dtelevision) normally transmits a drive signal (synchronization signal)specifying the timing of opening/closing the light shutters of theviewing device. Accordingly, when the reception portion of the viewingdevice does not receive the drive signal, the display device does notdisplay 3D images. In such a case, the power switch is automaticallyturned off, thereby preventing the secondary battery from beingdischarged completely in vain.

In yet another aspect of the present invention, the power source unit ofthe optical device includes a secondary battery with a small capacity of10 mAh to 100 mAh. Such a small-capacity secondary battery is prone tobe discharged completely with the power switch left on. Therefore, thepresent invention is advantageous particularly in such a case. In viewof this, when the power source unit includes a secondary battery with asmaller capacity of 10 mAh to 50 mAh for the purpose of weightreduction, the need to apply the present invention is further increased.

In yet another aspect of the present invention, the secondary battery ofthe optical device has a diameter or breadth of 2 mm to 6 mm. Byproviding the secondary battery in such an elongated cylindrical orrectangular shape, it is rendered possible for the secondary battery tobe readily built in the temple or suchlike. As a result, the flexibilityto arrange the secondary battery can be enhanced. In general,cylindrical or rectangular batteries include metal can casings. Inaddition, these shapes are resistant to an increase in internalpressure, and therefore a large amount of material can be accommodatedeven in a small volume. Moreover, high resistance to external forceprovides suitability for inclusion in flexible portions of the opticaldevice, such as temples and earpieces. Here, the term “rectangular”encompasses shapes where the cross section is elliptical or the crosssection includes a pair of straight segments and has arc-like portionson opposite sides. Herein, the breadth of the rectangular secondarybattery refers to the length of the major axis of the cross section.

The secondary battery is preferably included near the rear end of one ofthe pair of temples or in one of the pair of earpieces. As a result,weight balance of the optical device in which relatively heavy lenses,liquid-crystal light shutters, etc., are arranged on the front side canbe shifted to the rear side. Thus, the comfort of wearing the opticaldevice can be enhanced. In this case, for each of the temples, distanceL₂ between the front end of the temple and center of gravity G of theentire viewing device along a direction in which the temple extends ispreferably 15% to 50% of distance L₁ between the front end of the templeand the rear end of the earpiece along the direction in which the templeextends. As a result, the comfort of wearing can be remarkably improved.A more preferable range is from 20% to 35%. Note that the direction inwhich the temple extends refers to the direction of the temple in itsunfolded state.

As described above, the optical components of the present invention are,by way of example, liquid-crystal light shutters for viewing 3D images.In this case, the driver circuit drives the liquid-crystal lightshutters in synchronization with switching between two types of images,i.e., right-eye and left-eye images, alternatingly displayed on anexternal image display device. More specifically, the driver circuitapplies a variable voltage to each of the liquid-crystal light shuttersin synchronization with switching between two types of imagesalternatingly displayed on an external image display device, such thatwhen one of the liquid-crystal light shutters has high transparency, theother has low transparency, and when one liquid crystal light shutterhas low transparency, the other has high transparency.

In another example, each of the optical components of the presentinvention includes an electroactive material whose refractive indexvaries upon activation through application of a voltage greater than orequal to a predetermined value. In this case, the driver circuitactivates the electroactive material by applying the voltage greaterthan or equal to the predetermined value to the electroactive materialunder a predetermined condition. Here, for example, the predeterminedcondition refers to an instruction provided by the user's buttonoperation or an instruction from a sensor means for sensing the user'spredetermined action (e.g., the action of lowering the head). As theelectroactive material, a cholesteric liquid crystal material can beused, for example.

Embodiment 1

Hereinafter, a more specific embodiment of the present invention will bedescribed with reference to the drawings.

FIG. 1 is an oblique view of a stereoscopic image viewing device as anoptical device according to Embodiment 1 of the present invention. FIG.2 shows a functional block diagram of the stereoscopic image viewingdevice.

The stereoscopic image viewing device (referred to below as the viewingdevice) 10 is an eyewear-like viewing device compatible with anactive-shutter stereoscopic image viewing system.

The active-shutter stereoscopic image viewing system is a system forviewing stereoscopic images in which right-eye and left-eye images aredisplayed on a display device such as a 3D television while beingalternatingly switched at high speed, and light shutters of the viewingdevice 10 are alternatingly opened/closed in synchronization with theswitching of images on the display device.

In the viewing device 10, right-eye and left-eye light shutters 12 haveunillustrated electrodes connected to a driver circuit 14, which is inturn connected to a power source unit 16 for driving the light shutters12. The power source unit 16 includes a secondary battery 44, acharge/discharge circuit 30 for controlling charge and discharge of thesecondary battery 44, a power switch 38, a power switch control portion40, and a wear-sensing portion 42 for sensing the viewing device 10being worn by a user. Details of the power switch control portion 40 andthe wear-sensing portion 42 will be described later.

The charge/discharge circuit 30 is connected to the driver circuit 14via the power switch 38. The power switch 38 is connected to the powerswitch control portion 40, which is in turn connected to thewear-sensing portion 42. The charge/discharge circuit 30 is connected tothe secondary battery 44, and can be connected to an external powersource 32 such as a commercial power source.

The light shutters 12 are held by a pair of rims 18, respectively. Thepair of rims 18 are connected at their inside edges to each other via abridge 20. Each of the rims 18 is pivotably connected at its outsideedge to the front end of a temple 22 via a hinge 24. The temple 22 hasan earpiece 26 formed at the rear end. Each rim 18 has a nose pad 28formed near the bridge 20. The pair of rims 18, the bridge 20, thetemples 22, the hinges 24, the earpieces 26, and the nose pads 28constitute a frame 1.

The unillustrated display device (such as a 3D television) transmits asynchronization signal such as infrared (the signal being related todriving of optical components), which specifies the timing of openingand closing the light shutters 12. On the other hand, the bridge 20 isprovided with a reception portion 36 for receiving the synchronizationsignal. The reception portion 36 transmits the signal related to thetiming of opening/closing the light shutters 12 to the driver circuit 14on the basis of the received synchronization signal.

As the light shutters 12, liquid-crystal light shutters are preferablyused from the viewpoint of operation speed and quietness. Liquid-crystallight shutters operate so as to become transparent upon voltageapplication and opaque upon cessation of voltage application.

FIG. 3 is an oblique view of the appearance of a secondary battery. Thesecondary battery 44 has an elongated shape of 2 mm to 6 mm in diameteror width D and 15 mm to 35 mm in length L. As the secondary battery 44,a non-aqueous electrolyte secondary battery, in particular, alithium-ion secondary battery, is preferably used in view of high energydensity. Note that the secondary battery 44 is not limited to acylindrical shape as shown in the figure, and secondary batteries ofvarious shapes such as a rectangular shape can be used. In general,cylindrical or rectangular batteries include metal can casings. Inaddition, the term “rectangular” refers to a shape corresponding to arectangular battery as it is called in the field of battery, and thetube portion has at least a pair of parallel planes. The rectangularshape encompasses a thin flat shape with rounded edges. Moreover, thewidth of a rectangular secondary battery refers to the greater of thewidths where there are narrow and wide widths.

The secondary battery 44 is sized and shaped as mentioned above so thatit can be disposed near the rear end of the temple 22 or in the earpiece26 without sacrificing design.

Here, setting the secondary battery 44 to be 2 mm or more in diameter Dfacilitates easy manufacturing of the secondary battery 44 compared tothe case where diameter D is smaller, resulting in reduced productioncost. Moreover, it is ensured that the secondary battery 44 can have asatisfactory capacity. On the other hand, the reason for the secondarybattery 44 to be 6 mm or less in diameter D is to dispose the secondarybattery 44 at the rear of the viewing device more readily withoutcompromising design when compared to the case where diameter D isgreater.

Furthermore, using a secondary battery in the power source unit 16eliminates the need to frequently change the battery, resulting ineasier use of the viewing device 10. The capacity of the secondarybattery 44 can be in the range from 10 mAh to 100 mAh, for example. Thepresent invention produces a remarkable effect particularly in the casewhere the secondary battery 44 with such a small capacity is used. Inthe case where the capacity of the secondary battery 44 is in the rangefrom 10 mAh to 50 mAh, the need to apply the present invention ishigher.

As shown in FIG. 1, the viewing device 10 as illustrated has the drivercircuit 14 disposed near the rear end of the right temple 22 (on thedepth side of the figure) and the power source unit 16 disposed near therear end of the left temple 22 (on the front side of the figure). Thearrangement of the components is not limited to this, and at least oneor all of the constituent elements of the power source unit 16 and thedriver circuit 14 can be disposed at the left and right earpieces 26.

In an example, the power source unit 16 can be disposed in the earpiece26 which is positioned further rearward from the above rear end positionof the left temple 22, in order to achieve a right-left weight balancewith the driver circuit 14, which is relatively heavy. To allow suchweight balance to be distributed near the rear as much as possible, allof the constituent elements of the power source unit 16 and the drivercircuit 14 may be disposed in the earpieces 26.

Here, it is not requisite to dispose the driver circuit 14 and the powersource unit 16 entirely near the rear ends of the temples 22 or in theearpieces 26, and the driver circuit 14 and the power source unit 16 canbe disposed in part (e.g., the charge/discharge circuit) near the frontends of the temples 22 or in the rims. However, the secondary battery 44and the driver circuit 14 are relatively heavy and therefore preferablyprovided near the rear ends of the temples 22 or in the earpieces 26.

In this case, the driver circuit 14 and the power source unit 16 aredesirably positioned such that, where the distance between the front endof the temple 22 (e.g., the center point on the shaft of the hinge 24)and the tip of the earpiece 26 (the distance along the direction inwhich the temple extends) is taken as 100%, the center of gravity of theviewing device 10 is positioned at a distance of 15% to 50% from thefront end of the temple 22. When the center of gravity of the viewingdevice 10 is within the above range, the comfort of wearing the viewingdevice 10 is good.

FIG. 4 illustrates an exemplary housing portion for accommodating thedriver circuit and the power source unit. The housing portion 34 isformed as a hollow portion provided in each of the right and lefttemples 22, to accommodate the driver circuit 14 and the power sourceunit 16 within the temples 22. The housing portion 34 can be providedwith a lid that can be opened and closed.

The shape of the housing portion 34 is not limited to a rectangularshape as shown in the figure, and if the cross section of the temple 22is rounded, the housing portion 34 can be cylindrical or suchlikecorrespondingly. The size of the housing portion 34 is appropriately setin accordance with the size of a target to be accommodated therein.Alternatively, the housing portion 34 may be provided in the earpiece26.

The housing portion 34 is formed as a hollow portion provided in each ofthe temples 22 or the earpieces 26, so that portions of the drivercircuit 14 and the power source unit 16, in particular the secondarybattery 44, the size of which is relatively difficult to reduce, can beaccommodated within the temples 22 or the earpieces 26 without causingthe user to be aware of their presence. This broadens the choice ofdesigns of the viewing device 10, making it easy to improve theappearance.

Furthermore, since the power source unit 16 uses the secondary battery44 in place of a conventional primary battery, there is less need tochange the battery. Therefore, the power source unit 16 and the drivercircuit 14 may be built in the temples 22 or the earpieces 26 throughembedding by insert molding if the temples 22 or the earpieces 26 aremade of resin. This increases the flexibility in designing the viewingdevice.

Next, the power switch control portion 40 and the wear-sensing portion42 will be described in detail.

When the power switch 38 is on, i.e., the driver circuit 14 and thecharge/discharge circuit 30 are electrically connected to each other,and the wear-sensing portion 42 does not sense the viewing device 10being worn by a user, the power switch control portion 40 operates toturn off the power switch 38. The power switch control portion 40 thusoperating can be configured by a CPU (central processing unit) or an MPU(micro-processing unit), memory, and so on.

The wear-sensing portion 42 can be configured by a pyroelectric sensor.The pyroelectric sensor is provided in, for example, a portion of thetemple 22, the nose pad 28, or the earpiece 26 that touches the user'sskin. The wear-sensing portion 42 senses the viewing device 10 to beworn by the user when the temperature detected by the pyroelectricsensor is greater than or equal to a reference value (e.g., 34° C.)

Alternatively, the wear-sensing portion 42 can be configured by acapacitive sensor. The capacitive sensor is provided in, for example, aportion of the temple 22, the nose pad 28, or the earpiece 26 thattouches the user's skin. When the capacitance detected by the capacitivesensor changes by a prescribed value (absolute value) or more, thewear-sensing portion 42 senses whether or not the viewing device 10 isbeing worn by the user, on the basis of the direction of the change(either positive or negative).

Hereinafter, the operation of the power switch control portion 40 willbe described with reference to a flowchart of FIG. 5.

First, when the power switch 38 is turned on, a standby of a firstpredetermined period (e.g., 30 seconds) is taken (step S1). Thereafter,upon completion of the standby of the first predetermined period, it isdetermined whether or not the wear-sensing portion 42 has sensed theviewing device 10 being worn by a user (step S2). When the result ofdetermination is affirmative (Yes), a standby of a second predeterminedperiod (e.g., 5 seconds) is taken (step S3). Upon completion of thestandby, step S2 is performed again. Steps S2 and S3 will be repeateduntil the result of determination in step S2 turns negative (No). Thefirst predetermined period is set considering the time between the userturning on the power switch 38 and actually wearing the viewing device.The second predetermined period is set such that the determination isnot performed very frequently.

On the other hand, when the result of determination in step S2 isnegative (No), a standby of a third predetermined period (e.g., 30seconds) is taken (step S4). Upon completion of the standby, it isdetermined again whether the wear-sensing portion 42 has sensed theviewing device 10 being worn by a user (step S5). The thirdpredetermined period is set for the purpose of avoiding the viewingdevice being turned off instantly every time the user takes off theviewing device at the time of 3D-image viewing.

When the result of determination in step S5 is affirmative (Yes), astandby of the second predetermined period (e.g., 5 seconds) is taken(step S3), and step S2 is performed again thereafter. On the other hand,when the result of determination in step S5 is negative (No), the powerswitch 38 is turned off (step S6), thereby ending the process.

When the power switch 38 is on and the wear device 42 does not sense theviewing device 10 being worn by a user, the power switch 38 isautomatically turned off through the above process. Thus, the secondarybattery 44 is prevented from being discharged completely in vain,thereby prolonging the life of the secondary battery 44 or even theviewing device 10.

Embodiment 2

Next, Embodiment 2 of the present invention will be described.

The viewing device of Embodiment 2 is similar in appearance and circuitconfiguration to that of Embodiment 1, and therefore will be describedusing the same reference characters as in FIGS. 1 and 2.

FIGS. 6 and 7 schematically illustrate feature portions of Embodiment 2in enlargement. In Embodiment 2, each of the right and left hinges 24 isprovided with biasing means for biasing the temple 22 in a foldingdirection (e.g., a helical spring 23 or an elastic member such as a flatspring or rubber). In addition, a film-like piezoelectric sensor (piezofilm) 25 is provided near at least one of the hinges 24. In this case,the film is arranged such that the pressure applied to the piezoelectricsensor 23 when the temple 22 is folded (FIG. 7) is lower than thepressure applied to the piezoelectric sensor 23 when the temple 22 isnot folded (FIG. 6).

In the configuration described above, when the temples 22 are notfolded, the viewing device is considered as being worn by the user.Moreover, in this case, there is a greater difference in potentialbetween terminals of the piezoelectric sensor. On the other hand, whenthe temples 22 are folded, the viewing device is not considered as beingworn by the user. Moreover, in this case, there is only a slightdifference in potential between the terminals of the piezoelectricsensor. Thus, when the difference in potential between the terminals ofthe piezoelectric sensor is greater than a predetermined value, theviewing device is sensed as being worn by the user, whereas when thedifference in potential between the terminals of the piezoelectricsensor is less than the predetermined value, the viewing device issensed as not being worn by the user. That is, in Embodiment 2, thepiezoelectric sensor functions as a wear-sensing portion.

Therefore, it is possible to achieve a similar effect to that achievedby Embodiment 1 through a process similar to that shown in FIG. 5. Notethat the configuration for sensing whether the temples 22 are folded ornot is not limited to the above. For example, electrodes may be attachedto the temples 22 or the earpieces 26, and also to the rims 18 so as tocontact each other when the temples 22 are folded, and the temples 22may be determined to be folded when the electrodes can be electricallyconnected to each other.

Embodiment 3

Next, Embodiment 3 of the present invention will be described.

The viewing device of Embodiment 3 is similar in appearance to that ofEmbodiment 1, and therefore will be described using the same referencecharacters as in FIG. 1.

FIG. 8 illustrates a functional block diagram of the viewing device ofEmbodiment 3. In the viewing device 10A, the reception portion 36 isconnected to the power switch control portion 40, and the wear-sensingportion 42 is omitted from the power source unit 16A.

When the reception portion 36 receives a synchronization signal, andoutputs a signal based on the synchronization signal to the power switchcontrol portion 40, 3D images are presented on the display device.Accordingly, while the reception portion 36 is outputting a signal basedon a received synchronization signal, the viewing device 10A isconsidered as being in use by a user. On the other hand, while thereception portion 36 is not outputting a signal based on a receivedsynchronization signal, no 3D images are presented on the displaydevice, and therefore the viewing device 10A is not considered as beingin use by a user. That is, in Embodiment 3, the reception portion 36functions as a use-status sensing portion.

Furthermore, when the power switch 38 is on and the reception portion 36is not receiving a synchronization signal, i.e., the reception portion36 is not sensing the viewing device 10A being in use by the user, thepower switch control portion 40 operates to turn off the power switch38.

The operation of the power switch control portion 40 will be describedbelow with reference to a flowchart of FIG. 9.

First, once the power switch 38 is turned on, a standby of a firstpredetermined period (e.g., 30 seconds) is taken (step S11). Thereafter,upon completion of the standby of the first predetermined period, it isdetermined whether or not the reception portion 36 is receiving asynchronization signal (step S12). When the result of determination isaffirmative (Yes), a standby of a second predetermined period (e.g., 5seconds) is taken (step S13). Upon completion of the standby, step S12is performed again. Steps S12 and S13 will be repeated until the resultof determination in step S12 turns negative (No). The firstpredetermined period is set considering the time between the userturning on the power switch 38 and the display device actually startingto display 3D images. The second predetermined period is set such thatthe determination is not performed very frequently.

On the other hand, when the result of determination in step S12 isnegative (No), a standby of a third predetermined period (e.g., 3minutes) is taken (step S14). Upon completion of the standby, it isdetermined again whether or not the reception portion 36 is receiving asynchronization signal (step S15). The third predetermined period is setfor the purpose of avoiding the power being turned off instantly everytime 3D images, such as a CM (commercial message), are displayed, forexample.

When the result of determination in step S15 is affirmative (Yes), astandby of the second predetermined period (e.g., 5 seconds) is taken(step S13), and step S12 is performed again thereafter. On the otherhand, when the result of determination in step S15 is negative (No), thepower switch 38 is turned off (step S16), thereby ending the process.

When the power switch 38 is on and the reception portion 36 is notreceiving a synchronization signal, the power switch 38 is automaticallyturned off through the above process. Thus, the secondary battery 44 canbe prevented from being discharged completely in vain, therebyprolonging the life of the secondary battery 44 or even the viewingdevice 10A itself.

Embodiment 4

Next, Embodiment 4 of the present invention will be described.

FIG. 10 illustrates a lens for use in variable focus eyeglasses as anoptical device according to Embodiment 4, as viewed from a directionperpendicular to an incident direction of light. The appearance of thevariable focus eyeglasses themselves is similar to the viewing device inFIG. 1. Accordingly, descriptions of similar portions will be givenusing reference characters in FIG. 1. In addition, the thickness ratioand other ratios among the portions shown in FIG. 10 are different fromactualities for convenience of viewing.

The lens 50 illustrated in the figure includes a base lens 50 a, and aplanar electroactive element 51 embedded in the base lens 50 a. Forexample, a normal optical lens (concave lens) for myopia correction canbe used as the base lens 50 a. The electroactive element 51 is a devicehaving a refractive index variable in response to application ofelectrical energy. The electroactive element 51 is in opticalcommunication with the base lens 50 a. Such a lens 50 can be attached tothe frame 1 (more specifically, the rim 18) in FIG. 1. Note that theelectroactive element 51 can be attached to the surface of the base lens50 a, rather than in the inside.

The electroactive element 51 can be disposed across the entire orpartial field of view of the lens 50. In FIG. 10, long dasheddouble-short dashed lines indicate the electroactive element 51 beingdisposed across the entire field of view of the lens 50. Theelectroactive element 51 can be planar as illustrated in the figure orcan be bent along the curved surface of the lens. Moreover, theelectroactive element 50 can be disposed in each or only one of the pairof lenses 50. Moreover, the number of electroactive elements 50 disposedin the lens 50 is not limited to one. Two or more electroactive elements50 can be disposed in one lens 50. For example, each lens 50 can bemerely transparent without a refractive power for myopia or hyperopiacorrection, and can have disposed therein both an electroactive element50 that exerts a refractive power for myopia correction upon activationand an electroactive element 50 that exerts a refractive power forhyperopia correction upon activation.

When the electroactive element 51 is disposed over only a portion of theentire field of view of the lens 50, the position of the electroactiveelement 51 in the lens 50 is not specifically limited. In an example,the electroactive element 51 can be disposed in such a position thatoverlaps with the user's viewing direction when the user looks down,i.e., the electroactive element 51 can be provided in the center of alower part of the lens 50.

FIG. 11 illustrates a cross-sectional view of an exemplary electroactiveelement. In this figure, the thickness to width ratio of theelectroactive element 51 and the thickness ratio among the layers do notreflect actualities. In the figure, the electroactive element 51 ismainly enlarged in the thickness direction.

The electroactive element 51 illustrated in the figure includes twotransparent substrates 52 and an electroactive material 53 providedtherebetween and made of a thin layer of liquid crystal material. Thesubstrates 52 are formed so as to contain the electroactive material 53therebetween and ensure that the electroactive material 53 cannot leaktherefrom. The thickness of each substrate 52 is, for example, greaterthan 100 μm but less than 1 mm, preferably on the order of 250 μm. Thethickness of the electroactive material 53 can be, for example, lessthan 100 μm, preferably, less than 10 μm.

One of the two substrates 52 can form a part of the base lens 50 a. Insuch a case, one of the substrates 52 can be essentially thicker thanthe other. In such a mode, the substrate that forms a part of the baselens 50 a can have a thickness of on the order of 1 mm to 12 mm, forexample. The other substrate 52 can have a thickness greater than 100 μmbut less than 1 mm, preferably on the order of 250 μm.

The two substrates 52 can have the same refractive index. Theelectroactive material 53 can include liquid crystals. Liquid crystalshave a refractive index variable upon generation of electric fieldsacross the liquid crystals, and therefore are particularly suitable forthe electroactive material 53. The liquid crystal material is preferablyinsensitive to polarized light. As the liquid crystal material, acholesteric liquid crystal material can be appropriately used. Thecholesteric liquid crystal material can include nematic liquid crystalswith a birefringence of about 0.2 or more. The cholesteric liquidcrystal material can further include chiral dopants with a helicaltwisting power of about 1.1 (μm⁻¹) or more. The electroactive material53 can have an average refractive index approximately equal to theaforementioned refractive index.

Each substrate 52 has an optically transparent electrode 54 provided onits surface that contacts the electroactive material 53. Once theelectroactive material 53 is activated through voltage application bythe electrode 54, the refractive index of the electroactive material 53changes, so that optical characteristics, such as focal distance anddiffraction efficiency, of the electroactive material 53 change. Theelectrode 54 can include any known transparent conductive oxide (e.g.,ITO (indium tin oxide) or tin-doped indium oxide) or conducting organicmaterial (e.g., PEDOT: PSS(Poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate)), carbonnanotube, or the like), for example. The thickness of the electrode 54can be less than 1 μm, for example, preferably, less than 0.1 μm.

The electroactive element 51 can be switched between first and secondrefractive indices, and can have a first refractive power in an inactivestate where applied voltage is less than first predetermined value E₁and a second refractive power in an active state where applied voltageis greater than second predetermined value E₂ (E₂>E₁).

The electroactive element 51 can be configured so as not tosubstantially exert a refractive index power in the inactive state. Inother words, when a voltage of less than first predetermined value E₁ isapplied (or when substantially no voltage is applied), the electroactivematerial 53 can have substantially the same refractive index as thesubstrate 52. In such a case, the electroactive element 51 has asubstantially constant refractive index across its thickness, so thatthere is no change in the refractive index.

On the other hand, upon application of a sufficient voltage to cause thedirector of the cholesteric liquid crystal material included in theelectroactive material 53 to align parallel to an electric field to begenerated (the voltage exceeding second predetermined voltage E₂), forexample, the electroactive element 51 can be in an active state so as toincrease the refractive index. In other words, when a voltage exceedingsecond predetermined voltage E₂ is applied, the cholesteric liquidcrystal material can have a refractive index different from therefractive index of the substrate 52.

For example, when the user is engaged in a long-distance activity suchas driving a car, the electroactive element 51 is deactivated, so thatthe user can have appropriate correction for long distance by the baselens 50 a. On the other hand, when the user is engaged in a short ormiddle-distance activity such as reading a book or viewing a computerscreen, the electroactive element 51 is activated, so that the user canhave appropriate correction for short distance.

The cholesteric liquid crystal material included in the electroactivematerial 53 is essentially cholesteric (i.e., chiral or twisted) or itis formed by mixing nematic liquid crystals with a chiral twist agent.In the case of the latter approach, the resultant cholesteric liquidcrystals have many of the same properties as the original nematic liquidcrystals. For example, the resultant cholesteric liquid crystal materialcan have the same refractive index dispersion. Moreover, the resultantcholesteric liquid crystal material has the same normal and abnormalrefractive indices as the original nematic liquid crystals. More nematicmaterials are commercially available than cholesteric liquid crystals,and therefore the latter approach is preferable and offers greaterdesign flexibility.

The variable focus eyeglasses can include a driver circuit for applyinga predetermined voltage to each of the electrodes 54. The driver circuitis a similar driver circuit to the driver circuits 14 in Embodiments 1through 3, and can operate in such a manner as to apply a predeterminedvoltage to each of the electrodes 54 in accordance with the user'sbutton operation or suchlike or in accordance with a detection resultfor the user's predetermined action (e.g., the action of lowering thehead). Such a driver circuit can be provided in the temple 22 or theearpiece 26 in the same arrangement as the driver circuits 14 inEmbodiments 1 through 3.

The power conversion eyeglasses can further include a power source unitconnected to the driver circuit so as to be able to control theelectroactive element 51. The power source unit has similar componentsto those of the power source unit 16 in FIG. 2, and operates in asimilar manner. Thus, in the present embodiment, as in Embodiments 1through 3, when the power conversion eyeglasses are not sensed to be inuse by the user, power supply from the driver circuit to theelectroactive element 51 can be stopped. Such a power source unit can beprovided in the temple 22 or the earpiece 26 in the same arrangement asthe power source units 16 and 16A.

INDUSTRIAL APPLICABILITY

In the optical device of the present invention, the secondary batteryserving as a power source is not discharged completely in vain, andtherefore can have its life prolonged readily. Thus, it is useful foroptical devices with built-in secondary batteries, such as so-called 3Deyeglasses expected to be distributed as accessories of 3D televisionsand so on, and it is also useful for variable focus eyeglasses withtheir powers variable in accordance with electric power.

Although the present invention has been described in terms of thepresently preferred embodiments, it is to be understood that suchdisclosure is not to be interpreted as limiting. Various alterations andmodifications will no doubt become apparent to those skilled in the artto which the present invention pertains, after having read the abovedisclosure. Accordingly, it is intended that the appended claims beinterpreted as covering all alterations and modifications as fall withinthe true spirit and scope of the invention.

EXPLANATION OF REFERENCE NUMERALS

-   -   10, 10A stereoscopic image viewing device    -   12 light shutter    -   14 driver circuit    -   16 power source unit    -   22 temple    -   26 earpiece    -   30 charge/discharge circuit    -   34 housing portion    -   36 reception portion    -   38 power switch    -   40 power switch control portion    -   42 wear-sensing portion    -   44 secondary battery    -   50 lens    -   51 electroactive element    -   53 electroactive material

The invention claimed is:
 1. An optical device comprising: at least oneoptical component configured to be electrically actuated such that alight transmission state is variable; a driver circuit for the at leastone optical component; a power source unit for driving the at least oneoptical component; a pair of rims; a pair of temples having front andrear ends and connected at the front ends to their respective rims; anda pair of earpieces formed at the rear ends of their respective temples,the at least one optical component being supported by at least one ofthe rims, the power source unit including: a secondary battery; a powerswitch; a power switch control portion; and a use-status sensing portionfor sensing the status of use by a user of the optical device, and thepower switch control portion performing control to turn off the powerswitch when the use-status sensing portion does not sense any use by theuser of the optical device, wherein, the temples are connected to theirrespective rims via hinges, including biasing means for biasing at leastone of the temples such that an angular position of the at least one ofthe temples about the hinge coincides with a predetermined angularposition corresponding to the device's status of not being in use, theuse-status sensing portion includes a second sensing portion for sensingthe angular position of the at least one of the temples to coincide withthe predetermined angular position, and the power switch control portionturns off the power switch when the second sensing portion senses theangular position of the at least one of the temples to coincide with thepredetermined angular position.
 2. The optical device according to claim1, wherein, the use-status sensing portion includes a first sensingportion for sensing the optical device to be worn by the user, and thepower switch control portion turns off the power switch when the firstsensing portion does not sense the optical device being worn by theuser.
 3. The optical device according to claim 2, wherein the firstsensing portion includes a pyroelectric sensor.
 4. The optical deviceaccording to claim 2, wherein the first sensing portion includes acapacitive sensor.
 5. The optical device according to claim 1, whereinthe secondary battery has a capacity of 10 mAh to 100 mAh.
 6. Theoptical device according to claim 5, wherein the secondary battery is acylindrical secondary battery.
 7. The optical device according to claim1, wherein the secondary battery is included near the rear end of the atleast one of the temples or in one of the earpieces.
 8. The opticaldevice according to claim 7, wherein, for each of the temples, adistance between the front end of the temple and a center of gravityalong a direction in which the temple extends is 15% to 50% of adistance between the front end of the temple and the rear end of theearpiece along the direction in which the temple extends.
 9. The opticaldevice according to claim 1, further comprising a reception portion fora signal related to driving of the at least one optical component, theuse-status sensing portion including a third sensing portion for sensingwhether or not the reception portion is receiving the signal, and thepower switch control portion turning off the power switch when the thirdsensing portion does not sense the reception portion receiving thesignal.
 10. The optical device according to claim 1, wherein, the atleast one optical component is a pair of liquid-crystal light shuttersrespectively supported by the rims, and the driver circuit is configuredto apply a variable voltage to each of the liquid-crystal light shuttersin synchronization with switching between two types of imagesalternatingly displayed on an external image display device, such thatwhen one of the liquid-crystal light shutters has high transparency, theother has low transparency, and when one liquid crystal light shutterhas low transparency, the other has high transparency.
 11. The opticaldevice according to claim 1, wherein the at least one optical componentincludes an electroactive material whose refractive index varies uponactivation through application of a voltage greater than or equal to apredetermined value, and the driver circuit activates the electroactivematerial by applying thereto the voltage greater than or equal to thepredetermined value.
 12. The optical device in accordance with claim 1,wherein the use-status sensing portion senses that the angular positionof the at least one of the temples coincides with the predeterminedangular position, based on the biasing force of the biasing means. 13.The optical device in accordance with claim 12, wherein the use-statussensing portion further includes a piezoelectric sensor, and thepiezoelectric sensor senses the biasing force of the biasing means.